def show():
    student_new = []
    if os.path.exists(filename):
        with open(filename,'r') as rfile:
            student_old = rfile.readlines()
            for list in student_old:
                student_new.append(eval(list))
            if student_new:
                show_student(student_new)
    else:
        print("未保存数据信息")